Now I can run PHD guiding on the device from iPad or Android via a X windows program (iSSH for iPad). I am now writing a web application to control a DSLR camera and to view photos taken by the camera via a web browser on the device. And yes, Goto can be commanded from SkySafari

Wonderful stuff. First we had the rush of people planning to buy a Pi to use as a regular computer with little IT knowledge, and I was a bit concerned about how it would work out, but now I'm starting to see lots of really cool projects like this

Is it fast enough to handle the guiding software? I know the CPU in it is particularly weak (attempts to run linux with a GUI without GPU acceleration have been very painful!), but it's enough to handle a lot of stuff. And the GPU looks reasonably good, and could definitely take a lot of the load in a guiding app.

I am using a low-quality Class4 SD card to run Raspbian and it takes about 8 sec for a 2sec shot to complete a cycle. I will use a good Class 10 card and expect 2x-2.5x improvement. If I want more improvement, I may switch off image display during guiding in the source code because a graph can show guiding errors.

Now, I use a Sandisk 16GB Class 10 Extreme (45MB/s) SD card. I tested cycling shots with an exposure time of 1 sec. The time interval between shots (exposure+download+image display time) is about 3 sec. And for an exposure time of 2 sec, the time interval is about 4 sec.

ADDED NOTE (Aug 19): I could not reproduce the speed achieved above. I need to check!

I just added the plate-solving feature using the engine from astrometry.net which was capable to perform blind solving. After getting an image, I use plate-solving to find the exact pointing position and send the RA-DEC values to align a mount. The crosshair in Skysafari is automatically synced to the new position So, Goto can be done from SkySafari with high pointing accuracy.

I've finally got my Pi up and running in wifi master (AP) mode and have ser2net configured. I can't believe it was that easy -- to think I nearly bought a SkyFi for more than twice the price of the Pi!

This will be great for me as I'm usually stuck up on my apartment roof with a netbook. I'm slap bang in the middle of Shanghai and due to poor visibility and blocked view in various directions, I can't always align properly, and used to rely on "syncing" a lot using KStars / INDI, which was painfully slow and cumbersome on a netbook.

I've also been using gphoto2 for a while to control my DSLR, so I'll be doing that too.

I'm interested in the astrometry.net solver too, I wonder how that will work in my orange skies.

For autoguiding, I've added a piggyback mount to my ETX-125 and have a modified webcam, but have never been able to get a decent polar alignment, and the ETX mount isn't great anyway. With all the functionality sitting on the Pi however, it's one less item of faffing around to get set up, so I'm much more likely to try it now and succeed I think.

I wonder how a focuser would integrate into this setup -- I remember LibINDI allowed for controlling focusers. An ideal setup would be taking a few photos with gphoto2, and doing rinse-repeat trial & error autofocusing.

I plan to integrate my Pi in a project box with 12V / 5V PSU so I basically have everything contained in one box with one power plug. The dream setup would be an automated setup as the Autostar is so slow and archaic -- auto align, auto focus, Goto provided by Skysafari.

INDI supports some focusers: Robofocus, Meade, and JMI. "Semi-auto" focusing is possible. The focuser movement and camera exposure are done in a series. Then the star images are compared by a user. The focuser is commanded to move to the position of the sharpest star image.

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There is a feature to find a guide star automatically in the new version of Linguider. The feature is incorporated in PiAstroHub. A user can also manually select a guide star by clicking "Tool" in "Guide Star Selection". That will open another window to manually select a guide star.